The first human case of a new, more dangerous strain of mpox has been found in the UK, the UK Health Security Agency has said.

The new strain is different to the one that has been circulating at low levels in the UK since 2022, primarily amongst gay and bisexual men.

The new case was detected in London. The individual has been transferred to the Royal Free Hospital High Consequence Infectious Diseases unit. They had recently travelled to countries in Africa that are seeing cases of the dangerous strain. Close contacts of the case are being followed up.

Professor Susan Hopkins, chief medical adviser at UKHSA, insists that the risk to the wider population is low.

"This is the first time we have detected this Clade of mpox in the UK, though other cases have been confirmed abroad,” she said.

“The risk to the UK population remains low, and we are working rapidly to trace close contacts and reduce the risk of any potential spread. In accordance with established protocols, investigations are underway to learn how the individual acquired the infection and to assess whether there are any further associated cases.”

Steve Russell, NHS national director for vaccination and screening, added: “The NHS is fully prepared to respond to the first confirmed case of this clade of mpox.

“Since mpox first became present in England, local services have pulled out all the stops to vaccinate those eligible, with tens of thousands in priority groups having already come forward to get protected, and while the risk of catching mpox in the UK remains low, if required the NHS has plans in place to expand the roll out of vaccines quickly in line with supply.”

Symptoms and vaccination (Source: UKHSA)

Clade Ib mpox was detected by UKHSA using polymerase chain reaction (PCR) testing. It is initially being managed as a high consequence infectious disease whilst the agency learns more about the virus.

Common symptoms of mpox include a skin rash or pus-filled lesions which can last 2 to 4 weeks. It can also cause fever, headaches, muscle aches, back pain, low energy and swollen lymph nodes.

The infection can be passed on through close person-to-person contact with someone who has the infection or with infected animals and through contact with contaminated materials. Anyone with symptoms should continue to avoid contact with other people while symptoms persist.

The UK has an existing stock of mpox vaccines, and last month announced that further vaccines are being procured to support a routine immunisation programme to provide additional resilience. This is in line with more recent independent JCVI advice.

Clade Ib mpox has been widely circulating in the Democratic Republic of Congo. Recent months and have also seen cases reported in Burundi, Rwanda, Uganda, Kenya, Sweden, India and Germany.

Working alongside international partners, UKHSA has been monitoring Clade Ib mpox closely since the outbreak in DRC first emerged, publishing regular risk assessment updates.


A UKHSA Technical Briefing on scenarios and technical elements of preparedness and response for clade I, published 12th September 2024, may be found here: https://assets.publishing.service.gov.uk/media/66e83b367f20ecc7ec3aa1db/mpox-technical-briefing-9.pdf

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